The decay rate of a battery pack can depend on the state of charge (SOC) of the pack when it is in an idle period, particularly in hot climates. For example, the decay rate for a calendar life of a battery can differ by several factors depending on whether the batteries are idled at 0%, 50%, or 100% SOC. In the case where a cell contains mixed cathode materials of lithium nickel cobalt manganese oxide (NCM) and lithium manganese oxide (LMO or spinel), the decay rate has been found to be highest in the SOC regions of 40%-80%. Therefore, a need exists for a vehicle and a method for controlling a battery in a vehicle that modifies a battery SOC when it is determined that the battery is not immediately needed—e.g., when the vehicle is in a key-off state for a prolonged time—and it is further determined that the battery SOC is in a range that indicates a high decay rate.